Our overall objectives are to identify those components involved in host transcription which interact with page P22 gene products in order to insure normal phage development and to elucidate the molecular nature of these interactions. We intend to approach this problem first examining changes in RNA metabolism of Salmonella typhimurium induced by P22 infection and by studying the biochemistry of infection in certain host mutants which alter or block phage development. The transcription of host and phage RNA will be examined using pulse labeling techniques with 3H-uridine followed by RNA/DNA hybridization to either purified phage or host DNA. After the patterns of transcription have been characterized in normal lysogenic and lytic infections, we will characterize the patterns of transcription resulting using various host and phage mutants isolated in this laboratory which modify or block phage P22 development or which alter the course of host RNA synthesis after infection. We hope ultimately to find how specific gene products made by the host and the phage interact to produce the alterations in RNA synthesis observed after phage infection.